30 METALLIC OXIDES.
green oxide recently precipitated, with gen gas. The red oxide is not sensibly netic.
The quantity of oxygen in the red may be investigated in various ways, z is generally allowed that they all cone giving 42 on 100 iron. The one wb have used peculiarly, and prefer both foi and accuracy, is to find the quantity of muriatic acid gas necessary to saturate a portion of the green sulphate. I take f stance 100 measures of 1.149 green sulj which I know to contain 8 grains of oxide; this I find absorbs nearly 13 hn measures of oxynmriatic acid gas befoi acid smell is developed; the oxygen responding to this quantity of acid is k to be near 660 measures, = .88 grain. Vol.. 1, p. 308.) Hence, if 8: .88:: 128 or 128 black oxide acquire 14 or becom when converted into the red oxide, fact being established, I find it very c nient to make use of the oxvmuriate of instead of the acid gas, adopting the so of green sulphate of iron as a test < quantity of oxymuriatic acid in a giv< lume of any solution of oxymuriate of The quantity of oxygen in the red os